Combined X-ray diffraction and freeze-fracture studies are directed at relating the appearance of intramembrane particles and other fracture surface textures to the underlying molecular organization in reconstituted membranes. A wide range of protein-lipid interactions have been postulated to be present for the purified membrane proteins to be studied: cytochrome oxidase (large protein complex traverses membrane), cytochrome b5 (small hydrophobic portion associates with bilayer core), T(is) fragment of glycophorin (hydrophobic region resides totally within bilayer core), ligatin (surface protein attaches specific enzyme to membrane). High resolution electron density profiles on an absolute scale obtained by X-ray diffraction of oriented multilayers will be used to determine the distribution of protein in the bilayer. This information will be correlated to the distinctive features of the freeze-fracture faces which will be analyzed quantitatively using low-temperature X-ray diffraction to provide accurate spacing standards in multilamellar samples ultra-rapidly frozen in the absence of cryoprotectants. Freeze-fracture-etch and negative staining, where applicable, will be used to characterize the surface distribution of proteins. Information from complementary replicas and rotary shadowing will help evaluate the extent of plastic deformations and surface contamination.